Precast Column Poured Too Tall. How to Cut Down Properly? 1

[MindofBarca]

All,

Good afternoon.

I have a precast concrete question regarding a podium style (precast beams, column, and hollow core) for two stories with stick framing above. One column, in particular, was cast too long; the precaster would like to salvage it if at all possible.

The column needs to be cut down 6". The top of column has cast-in coil inserts for precast beams to attach to and the column base has pockets with a 1" thick baseplate to sit on four exposed rebar cast into the footing.

ACI 318-11 7.10.5.7 has the top/bot tightly spaced tie criteria. Which we have met on both top and bottom, but once you remove either the top or the bottom 6", the next tie is 12"+ away.

Any thoughts or ideas on how to circumnavigate this criterion and properly trim down this precast column 6"?

Thanks in advance!
MindofBarca

 

[hokie66]

Maybe you should saw all around the column far enough down to accommodate your connections, chip away the remaining concrete, and recast to the proper height incorporating all the required fitments and reinforcement. Or you could just make a new column with the correct dimensions this time.

 

[HTURKAK]

I would consider and investigate the trimming the top of the ftg rather than trimming PC column. I do not know the column- ftg conn detail but i assume it is worth to investigate if Six in. pocket can be chipped ..

You may provide some details to get better responds..







I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[JohnRwals]

You may trim the top, bottom or CIP concrete.
What are you concerned about mainly?
Structural integrity or connection capacity loss?

 

[Brad805]

A precast column is not a big cost to re-cast unless it is very odd. I doubt you can do much repairs before it makes more sense to cast a new one. I am assuming labor rates and equipment rental costs you might see in North America.

 

[JohnRwals]

Generally, tight schedule matters rather than cost.
Precast member itself may not be expensive.
But, erection or consecutive process schedule delay may be more critical and expensive.
In another word, structural engineers should know how to solve this issue;
cut or remake? where to cut? how to keep/repair lost connections?

 

[JLNJ]

The last time we had to modify a precast element, we had the precaster's engineer design and specify the corrections. Is this not possible in your situation?

 

[Brad805]

John, in cases where you only need to modify by 1" - 4" it is easy, but in others you typically start cutting off embedded items that are very difficult to repair. If you can repair using Hilti products or other items in stock, sure, one can save time fixing, but if you need any special bonding agents you will find the same problem with time. Years ago I had to fix a column where a corbel was cast wrong. That was awful. Most can setup a form for a regular column in a few hours and cast the next day. It is pretty easy to get your concrete strength suitable for common construction loads by the next morning.